JPS59130568A - Formation of surface protective layer - Google Patents

Abstract

PURPOSE:To prevent the damage on a surface by coating a photocurable self- adhesive compsn. consisting of a low-mol.wt. polymer having 3,000-5,000 weight average mol.wt., a cross-linking agent and a photopolymerizable compd. on the surface and irradiating light thereto. CONSTITUTION:A monomer having active hydrogen, such as hydroxyethyl (meth) acrylate, and a monomer such as acrylonitrile are copolymerized in the presence of a radical initiator, and a copolymer having 3,000-50,000 weight average mol.wt. [hereunder expressed as a component (a)] is obtd. 0.1-15pts.wt. Cross- linking agent (for example, tolylene-2,4-diisocyanate, tolylene-2,6-dissocyanate, etc.) basing on 100pts.wt. the component (a) is mixed with said component. A photopolymerizable compd. such as 1,4-butylene glycol (meth)acrylate [component (c)] is compounded therewith at 10-80wt% total weight of the component (a) and the component (c). Said compounds is coated 1-100mum thickness on a sheet and light is irradiated thereto to cure the coating.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a surface protective layer on the surface of an adherend, and more specifically, it relates to a method for forming a surface protective layer on an adherend, and more specifically, it relates to a method for forming a surface protective layer on an adherend, and more specifically, it relates to a method for forming a surface protective layer on a surface of an adherend. The present invention provides a method for forming a surface protective layer for semi-permanently preventing damage to the surface of an adherend.

Conventionally, the surface protection of adherends such as plate-shaped articles has been carried out by temporarily attaching a surface protection adhesive film before processing, and then applying paint etc. after processing. is common.

These series of steps start with pasting the film onto a plate-shaped article, then undergo processing such as bending, drawing, and punching, followed by film peeling, surface cleaning, painting,
It consists of a drying process, which is not only complicated, but also
Since cleaning fluids and paints rarely contain large amounts of organic solvents, there have been various safety and hygiene problems.

Therefore, a first object of the present invention is to provide a method for forming a surface protective layer that can easily protect the surface of a plate-shaped article before processing and after processing.

A second object of the present invention is to provide a method for forming a surface protective layer by a simple operation without using an organic solvent during construction.

That is, the present invention provides: a) a monomer having an active hydrogen that can contribute to crosslinking and a monomer copolymerizable with the monomer and having a weight average molecular weight of 3,000 to 50,000; low molecular weight polymer C
(hereinafter referred to as component C); b) a crosslinking agent capable of reacting with active hydrogen in the low molecular weight polymer; C) a photopolymerization agent having at least one (meth)acryloyl group in the molecule; A composite obtained by applying a photocurable adhesive composition containing a chemical compound C (hereinafter referred to as component C) and a photosensitizer to the surface of a self-supporting sheet (or film) to form a photocurable adhesive layer. A sheet (or film) is laminated onto the surface of the adherend via the photocurable adhesive layer, the photocurable adhesive layer is cured by backlight irradiation, and then the self-supporting sheet (or film) The present invention relates to a method for forming a surface protective layer, which comprises peeling off only the adherend, and forming a surface protective layer made of a polymerized and cured product on the surface of the adherend.

According to the method of the present invention, damage to the surface of an adherend consisting of a plate-like article before and during processing is prevented by pasting a composite sheet, and after processing, it is irradiated with light. Since the surface of the adherend is protected by the surface protective layer formed by polymerizing and curing the curable adhesive layer, the surface of the adherend will not be damaged.

Monomers having active hydrogen that can contribute to crosslinking and are used to obtain component C in the photocurable adhesive layer used in carrying out this invention include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, Hydroxyl group-containing monomers such as allyl alcohol, monoesters of polyethylene glycol and (meth)acrylic acid, ethylene glycol or monovinyl ether of polyethylene glycol, monovinyl ether of propylene gelicol or polypropylene glycol,
Monomers containing primary or secondary amino groups such as aminoethyl (meth)acrylate, N-methylaminoethyl (meth)acrylate, N-ethylaminoethyl (meth)acrylate, acrylic acid, methacrylic acid, fumaric acid, itacon Examples include acids, carboxyl group-containing monomers such as allyl acetic acid, and one or more of these are used.

Further, as a monomer copolymerizable with the monomer having active hydrogen used to obtain component C, a (meth)acrylic acid ester in which the alkyl group has 1 to 12 carbon atoms is preferable. Others vinyl acetate, vinylpyridine, acrylonitrile, methacrylonitrile, acrylamide,
Examples include diacetone acrylamide, styrene, etc.
One or more of these may be used.

Component C is obtained by copolymerizing 1 to 30 parts by weight of the monomer having active hydrogen described above and 99 to 70 parts by weight of a monomer copolymerizable with the above monomer.

To copolymerize the above monomers, a conventional radical initiator, a peroxide such as benzoyl peroxide, methyl ethyl ketone peroxide, acetyl peroxide, lauroyl peroxide, cumene hydroperoxide, α・α-azobis Isobutyronitrile, α
・Weight of the copolymer obtained by using an azo initiator such as α-azobiscyanovaleric acid in the presence of a mercaptan such as thioglycolic acid, 2-mercaptoethanol, or a chain transfer agent such as carbon tetrachloride. Average molecular weight is 3.0
00 to 50,000.

The copolymerization is preferably carried out without using a solvent or diluent, that is, by bulk polymerization, but ordinary solution polymerization may also be used.

The crosslinking agent capable of reacting with the active hydrogen in component B, that is, component C, has sufficient film-forming ability for the photocurable adhesive layer formed by forming a self-supporting sheet of the photocurable adhesive composition. and to provide sufficient adhesive properties before photocuring.

Such crosslinking agents include tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, diphenylmethane-4,4-diisocyanate, naphthylene-1,5-diisocyanate, trimethylolpropane and tolylene diisocyanates. :3 (molar ratio) adducts, incyanate group-containing compounds such as reaction products of polyhydric alcohols such as polyethylene glycol or polypropylene glycol and tolylene diisocyanates, neopentyl glycol diglycidyl ether,
Epoxy group-containing compounds such as trimethylolpropane polyglycidyl ether, bisphenol-based epoxy resin, trimethylolpropane tris(2-aziridinylpropionate), 1,1'-(4-methyl-m-phenylene)-bis- 3,3-aziridinyl urea, 1,1'-
Examples include aziridinyl group-containing compounds such as (hexamethylene)-bis-3,3-aziridinyl urea and ethylenebis(2-aziridinylpropionate), and one or more of these may be used.

The amount of component b to be used is in the range of 0.1 to 15 parts by weight per 100 parts by weight of component a. If it is less than 0.1 part by weight, the expected effect will not be obtained, and if it exceeds 15 parts by weight, The adhesive layer becomes too hard and the adhesive properties decrease.

Component C, that is, a photopolymerizable compound having at least one (meth)acryloyl group in the molecule (or at least one methacryloyl group or acryloyl group as a polymerizable double bond in the molecule, preferably Polyfunctional ones having two or more, such as Eva, 1,4-butylene glycol (meth)acrylate, 1,6-hexane gelyl di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol Examples include monomers such as resin (meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethanetetra(meth)acrylate, and oligomers such as epoxy acrylate, urethane-modified acrylate, and oligoester acrylate. Two or more types may be used in combination if necessary.

The blending ratio of component C is 10 in the total amount of component a and component C.
-80% by weight, preferably 30-70% by weight; if the blending ratio of component C in the total amount exceeds 80% by weight, the cohesiveness of the photocurable adhesive layer before light irradiation will be poor, resulting in side effects. This is undesirable as it may cause glue to ooze out. Further, if it is less than 10% by weight, sufficient curing cannot be obtained, which is not preferable.

The photosensitizer is not particularly limited as long as it accelerates the photopolymerization reaction of the component C, but examples include benzoin, such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and α-methylbenzoin. anthraquinones such as 1-chloroanthraquinone, 2-chloroanthraquinone,
Examples include benzophenones such as benzophenone, P-chlorobenzophenone, and P-dimethylaminobenzophenone, and ion-containing compounds such as diphenyl disulfide and tetramethylthiuram disulfide.

The photosensitizer is 0.05 to 20 parts by weight, preferably 0.5 to 20 parts by weight, based on 100 parts by weight of the total amount of component a and component C.
They are mixed in a range of 10 parts by weight.

Appropriate amounts of other compounding agents can be added to this photocurable pressure-sensitive adhesive composition depending on the purpose. Examples of compounding agents include polymerization inhibitors that prevent thermal polymerization during production and reactions during storage, such as hydroquinone, hydroquinone monomethyl ether, tert-butylcatechol, P-benzoquinone,
2.5 = tert-butylhydroquinone, phenothiazine, etc., pigments for coloring or decoration such as zinc white, yellow lead, red iron oxide, dyes such as toluidine red, phthalocyanine blue, phthalocyanine green, other metal powders, glass peas , glass powder, glass flakes, etc., and tackifying resins such as xylene resins for the purpose of improving adhesive strength to the adherend surface.

In the method of the present invention, the photocurable adhesive composition is a colored or colorless transparent self-supporting sheet (or film) that transmits light, such as a polyvinyl chloride sheet or film, a polyolefin sheet or film (ethylene- (including sheets or films made of vinyl acetate copolymers and their saponified products), polyester sheets or films (
The photocurable pressure-sensitive adhesive layer is coated or transferred to a thickness of about 1 to 100 μm on one side (preferably 10 to 300 μm) to form a photocurable pressure-sensitive adhesive layer.

A composite sheet (or film) composed of a self-supporting sheet (or film) and a photocurable adhesive layer configured in this way can be used in the form of a plate made of a metal plate, glass plate, wood plate, decorative board, plastic plate, etc. It is attached to the surface of an adherend such as an article via an adhesive layer.

In order to polymerize and harden the adhesive layer, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, a carbon arc lamp,
Light irradiation is performed using a light source such as a xenon lamp for 0.3 seconds or more, preferably for 3 seconds or more. Note that the timing of the light irradiation may be before or after processing the adherend depending on the purpose.

After light irradiation, by peeling off only the self-supporting sheet (or film), a surface protective layer made of a polymerized cured product is formed on the adherend surface.Due to curing, the adhesive layer loses its plastic fluidity. Therefore, the sheet (or film) can be easily peeled off.

As described above, according to the method of the present invention, the composite sheet used for surface protection of the adherend is irradiated with light and the self-supporting sheet is peeled off, thereby forming a surface protective layer that can semi-permanently protect the surface. can be formed. Of course, the method of the present invention is related to the processing of adherends (or can be used simply to form a surface protective layer on the surface of an article).

Next, examples of this invention will be shown. In the following, "part" means part by weight, and "Mw" means weight average molecular weight.

Example 1 2-Ethylhexyl acrylate 50 parts Methyl methacrylate 43 parts 2-Hydroxyethyl methacrylate 7 parts 2-Mercaptoethanol? 1 part of the above blended composition and 0.2 parts of benzoyl peroxide were placed in a flask and stirred at 40°C for 30 minutes under a nitrogen atmosphere, then the temperature was raised to 80°C to remove the remainder of the above blended composition. was added dropwise over 2 hours, and the temperature was kept at 80°C for 2 hours to obtain a viscous copolymer (MW 6,000).

Next, to 50 parts of this copolymer, 5 parts of a reaction product of 3 moles of tolylene diisocyanate and 1 mole of trimethylol dimethacrylate, 1-50 parts of tetraethylene glycol dimethacrylate, and benzophenol 3 parts of hydroquinone and 0.00 of hydroquinone were mixed uniformly to prepare a photocurable pressure-sensitive adhesive composition.

This photocurable adhesive composition is applied to one side of a polyethylene sheet with a thickness of 60 μm so that the thickness after drying is 20 μm, and the photocurable adhesive composition is dried at 80° C. for 5 minutes to form a photocurable adhesive layer. A composite sheet was obtained.

This composite sheet is made of BA finished stainless steel plate 5O5304.
After pasting it on the adhesive layer, a high-pressure mercury lamp (8
The adhesive layer was cured by irradiating ultraviolet rays at a distance of 10 cm for about 5 seconds at 0 W/cm/1 lamp, and then only the polyethylene sheet was peeled off, and a surface protection made of a cured acrylic polymer was placed on the stainless steel plate. formed a layer.

Example 2 Vinyl acetate 30 parts Ethyl acrylate 60 parts Methacrylic acid
1 part lauryl mercaptan
A viscous copolymer (Mw s, o OO) was obtained in the same manner as in Example 1 using 3 parts of the above composition and 0.2 parts of azobisisobutyronitrile.

Next, to 70 parts of this copolymer, 7 parts of bisphenol type epoxy resin (Mw470) and 0.00 parts of tributylamine were added.
2 parts of trimethylolpropane triacrylate, 3 parts of 1-hydroxycyclohexylphenyl ketone, and 0.005 parts of hydroquinone were mixed uniformly to prepare a photocurable pressure-sensitive adhesive composition.

A surface protective layer was formed in the same manner as in Example 1 using this photocurable adhesive composition. However, a polyvinyl chloride sheet was used instead of the polyethylene sheet as the self-supporting sheet, and the drying temperature was 120°C.

Example 3 Acrylonitrile 80 parts Phthyl methacrylate 15 parts Methacrylic acid 5 parts Thioglycolic acid 2 parts A viscous material was prepared in the same manner as in Example 1 using the above composition and 0.2 parts of azobisisobutyronitrile. Copolymer (MW6,00
0) was obtained.

Next, to 60 parts of this copolymer, 5 parts of trimethylolpropane tris(2-aziridinylpropionate), 40 parts of tetramethylolmethanetetramethacrylate, 3 parts of benzyl dimethyl ketal, and 0.0 parts of hydroquinone.
005 parts were uniformly mixed to prepare a photocurable pressure-sensitive adhesive composition.

A surface protective layer was formed in the same manner as in Example 1 using this photocurable adhesive composition.

The results of measuring the pencil hardness and adhesion of the surface protective layers obtained in Examples 1 to 3 above are shown in the following table.

In addition, regarding the adhesion strength, the values are also shown when the adherends are copper plates and acrylic plates, and the surface protection layers are formed by grinding in the same manner as in Examples 1 to 3.

In addition, we investigated the adhesive strength of the composite sheet before light irradiation (initial adhesive strength) and the adhesive strength (self-supporting sheet peeling force) when peeling the self-supporting sheet one layer after light irradiation (Gotsushi). The results are also listed in the table below.

Note that the above measurements were performed by the following method.

Initial adhesion strength: The composite sheet was cut into two widths, pasted on a BA finished stainless steel plate SUS 3Q4, left for 30 minutes, and then peeled off at 180 degrees and the adhesive strength was measured.c Peeling speed: 30 Qg/min, 20°C ×65%k.

Hl).

Self-supporting sheet peeling force: After cutting the composite sheet into a 25 m width and pasting it on a BA finished stainless steel plate SUS 3Q4, it was irradiated with ultraviolet rays for about 5 seconds from a distance of 10 pieces using a high pressure mercury lamp (80 W/cm / 1 lamp). , the 180 degree peel adhesive force of the self-supporting sheet T was measured at a peeling speed of 300 r.
ttn/m”n, 20°C x 65% R,H,).

Pencil hardness: The hardness of the surface protective layer was measured according to JIS K 5400.

Adhesion: 100 cuts with a spacing of 1 m 17+ were made in the shape of a base grid on the surface protective layer, a commercially available cellophane adhesive tape was pasted thereon, the tape was then peeled off, and the percentage of the base grids remaining was expressed.

As is clear from the above examples, it can be seen that according to the method of the present invention, a good surface protective layer can be easily formed on an adherend.

Claims (1)

[Claims] fl) a) A weight average molecular weight of 3,000 to 50 obtained by copolymerizing a monomer having active hydrogen that can contribute to crosslinking and a monomer copolymerizable with the monomer. ,000 low molecular weight polymer; b) a crosslinking agent capable of reacting with the active hydrogen in the low molecular weight polymer; A photocurable adhesive composition containing a sensitizer is applied to nine sides of a self-supporting sheet (or film) to form a photocurable adhesive layer, and a composite sheet (or film) is placed on the adherend surface. The photocurable adhesive layer is pasted together via the photocurable adhesive layer, and the photocurable adhesive layer is cured by backlight irradiation. Then, only the self-supporting sheet (or film) is peeled off, and polymerization is applied to the surface of the adherend. A method for forming a surface protective layer, which comprises forming a surface protective layer made of a cured product.